Isolation and characterization of the active product of B. pertussis which induces lymphocytosis is being pursued. The interaction between lymphocytosis-promoting factor (LPF) and lymphoid cells is being examined with respect to receptor-sites, kinetics, and effect on cell function. LPF is labelled with I125 and its fate and distribution within the intact animal will be followed. Chemical and immunochemical characterization of LPF are planned. The nature of the adjuvant principle of B. pertussis is to be determined. Fractions of culture supernatant fluids as well as extracts from whole organisms, including endotoxin, will be tested for their ability to act as adjuvants.